A plane type electric precipitator includes an electrode plate of plane shape, made of electricity-conducting material; a collecting plate, parallel to the electrode plate and made of electricity-conducting material; a plurality of electrode units, placed on the electrode plate and having tips; wherein direct electric voltage is applied between the electrode plate and the collecting plate, so that air passing through is exposed to high electric fields close to the tips of the electrode units, ionizing suspended particles and trapping ionized particles at the collecting plate, so that an air-cleaning effect results.